Classically, the transfer of provisions and equipment between two moving ships at sea has been accomplished primarily through utilization of a high line transfer system. In this system the provisions and equipment are placed on a trolley which has been suspended from a high line rig and which is moved between the two ships by means of a transfer cable driven by an inhaul winch and an outhaul winch which are located on the supply ship. The high line transfer system has been automated to a high degree. An operator at a control console on the supply ship may set a desired transfer velocity for the trolley as it moves between the ships, a desired landing velocity for the trolley as it approaches a ship, and set the system in an automatic mode in which it will automatically accelerate the trolley to the set transfer velocity and drive the trolley at that velocity until it reaches a specified distance from a ship at which point it will reduce the trolley velocity to the set landing velocity which will be the speed of the trolley when it strikes the landing post of the ship it is approaching. See U.S. Pat. No. 3,361,080 entitled "Method and Apparatus for Replenishment at Sea" and assigned in common herewith.
When the trolley has a heavy load the transfer and landing velocities are set relatively low so that the abrupt speed change which occurs between these velocities does not induce excessive shock into the transfer system which may cause the transfer cable to break or another system component to fail, and so that the loaded trolley does not swing. Additionally, the landing velocity is set low so that the trolley does not strike the landing post with excessive force. The landing force becomes important, particularly when the trolley is loaded with munitions or with delicate electronic gear which may be damaged by being subjected to excessive shock forces. Also, the control system has a fixed high rate of acceleration for the trolley. This rate is designed to ensure that the trolley is not struck by the ship it is departing. Because the rate must accommodate the worst possible situation it is greater than necessary in many instances.
The control console for the high line transfer system utilizes circular analog dial-type gauges to indicate the velocity of the trolley with respect to the ship it is approaching and to indicate the distance of the trolley from the supply ship and from the receiver ship. These gauges enable an operator to monitor the travel of the trolley as it moves between the ships. The operator is dependent upon these gauges for determining the location and velocity of the trolley especially at night when the trolley may not be visible from the control console.
It has been found desirable to provide a control system for operating the inhaul winch and the outhaul winch of a high line transfer system in which the rate of change of velocity of the trolley between the set landing velocity and the set transfer velocity is set to ensure that a minimum shock load is imposed upon the system. This set rate is maintained regardless of the set landing and transfer velocities. Also, it has been found desirable to provide a control system which will make the rate of acceleration of the trolley relative to the ship the trolley is leaving so that the rate of acceleration is sufficient to prevent the trolley from being bumped by the ship but is not excessive. Furthermore, the control system also should automatically change the velocity of the trolley from the set landing velocity to a preset terminal velocity to reduce the force with which the trolley strikes the landing post.
Additionally, it has been found desirable to provide a more easily readable visual indication of the distance the trolley is from both the transfer and the receiver ships and of the speed of the trolley with respect to the ship it is approaching. Furthermore, it has been found advantageous to provide a graphic display of the relative distance of the trolley from both ships and to provide an enhanced graphic illustration of the velocity of the trolley when it is close to a ship.